The use of radiation to treat various illnesses and maladies comprises a known area of endeavor. A corresponding radiation-treatment plan typically informs and guides the administration of radiation for such purposes. These plans often serve to provide a therapeutically-useful dose to a given treatment volume (such as, for example, a tumor) while attempting to minimize dosing non-targeted regions (such as adjacent healthy tissue) beyond some threshold. Dose-volume histograms (frequently denoted by the acronym “DVH”) are often employed to inform the development of such radiation-treatment plans.
It is also known that hot and cold spots (i.e., areas where dosing is “excessive” in that the dosing is either too much or inadequate, respectively) can occur in practice. The location and size of such spots typically depends, at least in part, upon geometric and dosimetric constraints as pertain to a given optimized application setting. Hot and cold spots are undesirable. Dose-volume histogram constraints are often employed to attempt to minimize the occurrence or severity of hot and cold spots. For example, traditional dose-volume histogram constraints penalize the objective function when a particular volume fraction is exceeded at a given dose. Unfortunately, volume fraction and dosing are often difficult to accurately predict in many application settings.
As a result, it remains a difficult challenge to adequately control hot and cold spots using traditional approaches. If the constraint is set too tightly (regarding weight and/or volume percentages) other aspects of the treatment can suffer. Conversely, if the constraint is set too loosely, hot or cold spots can appear.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.